Method of making closure caps



June- 30, 1942. .1. c. GIBBS METHOD OF MAKING CLOSURE CAPS Filed Dec. 1, 1938 JOM a @3233 Patented June 30, 1942 METHOD OF MAKING CLOSURE CAPS John 0. Gibbs, Brooklyn, N. Y., assignor to Anchor Cap is Closure Corporation, Long Island City, N. Y., a corporation of New York Application December 1, 1938, Serial No. 243,336

3 Claims.

The present invention relates to the sealing art and more particularly to a method of making a screw cap.

Screw caps fall into two general classes; first, continuous thread caps which have a spiral thread of one or more convolutions in the cap adapted to cooperate with a corresponding thread on a glass container; and second, lug caps which have a plurality of screw lugs formed in the skirt of the cap to cooperate with a corresponding number of lugs or projections on the container.

from being visible from the exterior of the cap.

The present invention relates more particularly to the latter class of screw caps and to a method of making them.

Lug caps have certain advantages over continuous thread screw caps in several particulars. Lug caps are easier to apply and remove, requiring, with a two lug cap, about one-half a turn, and with a four lug cap about one-quarter of a turn; whereas a continuous thread cap requires a a full turn or more. In addition, the thread of a continuous thread cap has a greater tendency to rust or freeze to the thread of the container. Also, the slope of the thread is so slight that the cap is difllcult to remove. Lug caps form a better seal than continuous thread caps, due to the uniform pressure applied at a plurality of points to compress the liner or other sealing member. On the other hand, due to the concentrated pressure on the glass container at the lugs of the closure, there is a greater tendency for the thread thereon to break under severe sealing strain. In addition, the manufacturing tolerance in the manufacture of the glass container must be adhered to more rigidly. In the event that glass having an excessive tolerance reaches the packer, and in some cases with glass within the prescribed tolerances, there may be difliculty in obtaining good seals, without undue breakage. It has been diflicult also to get the lugs forced sufllciently far inwardly with respect to the skirt of the cap to obtain a secure grip under the thread on the container to prevent the lugs from riding over the container thread in the sealing operation. Irregularities in the closure occasioned by striking in the lugs, impair the appearance of lug caps.

The present invention aims to eliminate or minimize the above difilculties experienced with lug caps by improving the strength of the lug and at the same time increasing its resiliency, by increasing the distance the lug projects inwardly, by minimizing the deformation of the cap in the lug forming operation, and by preventmethodof making closure caps which results in a closure with the above advantages and which minimizes the strain on the metal in the manufacture thereof.

An object of the present invention is to provide an improved method of manufacturing closure caps of the lug type.

Another object of the invention is to form a lug on a closure cap having greater strength and also greater resiliency.

Another object of the invention is to increase the strength of lugs on closure caps without im pairing their resiliency.

Another object of the invention is to increase the extent to which the lugs project inwardly with respect to the closure cap.

Another object of the invention is to minimize the deformation of the shirt oi the cap in the vicinity of the lugs.

Another object of the invention is to provide an improved method of forming lug caps having greater lug resiliency and greater inward projection without marring the skirt of the cap above the bead.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and description and is shown in the accompanying drawing, forming a part of the specification, wherein Fig. 1 is a side elevational view of a closure cap sealed to a container with portions broken away to illustrate the engagement of one of the cap lugs with a thread on the container;

Fig. 2 is a sectional view illustrating the first step in the method of manufacturing the closure;

Fig. 3 is an enlarged fragmentary sectional view illustrating the second step in the manufacture of the closure;

Fig. 4 is an enlarged fragmentary sectional view illustrating the third step in the manufacture oi the closure;

Fig. 5 is an enlarged fragmentary sectional view illustrating the formation of the lug which is the fourth step in the manufacture of the closure;

ing the lacquer coating on the inside of the cap Fig. 5a is an enlarged fragmentary sectional view illustrating the closure of Fig. 5 applied to a container;

Fig. 6 is a sectional view on the line tlof Fig. 5 illustrating details of the lug construction;

Fig. 7 is a sectional view on the line 3-4! of Fig. 5 illustrating details of the lug construction; and

Fig. 8 is an enlarged fragmentary sectional view through the lug of the closure illustrating a modified form of lug construction.

Referring again to the drawing, the general construction of the closure and container are shown in Fig. l, in which a glass container l is sealed with a lug Closure 2 embodying the present invention. lhe closure 2 has a cover portion 6 and a depending skirt 7. The lower edge of the skirt of the cap is set outwardly and turned inwardly with lugs 5 formed therefrom to engage the projections l on the container when the cap is screwed down to compress a sealing liner 8 for sealing the rim of the container. The construction of the closure cap and the lug construction will be described in detail in connection with the preferred method of making the closure.

Referring more particularly to Figs. 2 to 5 illustrating the several steps in the method of manufacturing the cap, the first step of which is illustrated in Fig. 2. A plain coated or lacquered sheet of tinplate is placed in a stamping machine and a circular disc is cut out by a stamping die and preferably simultaneously formed into a cup shaped blank, as shown in Fig. 2. Two steps may be utilized in arriving at the blank shown in Fig. 2, but preferably a combination die is used to cut and shape the cup shaped blank in a single operation. The blank comprises a cover portion E having a bead El therein which presents a substantially flat surface on its underside adapted to overlie the rim of the container. Preferably the width of the underside of the bead is suificient to compress the gasket 8 over substantially the entire width of the rim. The cover is preferably domed as shown in Figs. 2 to 5a although any desired shape of cover may be utilized. The beaded cover construction is preferred because it stififens the cover of the cap. The cover retains flexibility but requires a greater force to flex it. It is like replacing a Weak spring with a strong one. The skirt i depends downwardly from the cover portion, and has a substantially cylindrical upper part with a substantially cylindrical band in adjacent the lower edge thereof offset outwardly with respect to the main portion of the skirt. The band ill, as will be noted, has a greater diameter than the skirt above the band.

The second step in the operation of forming the cap, is to turn inwardly the lower edge of the band it, as shown at M in Fig. 3. The purpose of turning this inner edge in is to facilitate the third manufacturing step, about to be described.

The third step is illustrated in Fig. 4 and comprises the formation of the inturned head it. The inturned edge ii is forced further inwardly and upwardly by a spinning or bumping operation into the form illustrated at iii in Fig. 3. The inturned edge it prevents any possibility of the skirt of the cap collapsing or of the lower edge of the cap being rolled outwardly during the forming operation. It will be noted that the finished head on the closure has an external diameter substantially greater than the external diameter of the closure above the bead. The

aasaaeo head has an internal diameter substantially equal to the internal diameter of the closure above the head, that is, the inner part of the bead is substantially in line with the inner side of the skirt of the cap. The advantages of the construction described will be pointed out more particularly in the description of the lug construction.

The lugs 5) are formed in the blank shown in Fig. 4, by striking inwardly and upwardly the head 62 at intervals about the circumference thereof, as shown more particularly in Figs. 5, 6 and 7, where it will be noted that the bead i2 is struck inwardly and that the external diameter of the bead at the lugs is substantially equal to the external diameter of the cap above the lugs, as shown at Hi. In addition, the bead is forced upwardly, as shown at iii (Fig. 7) to provide an arch construction. It will be noted also that the upper side it of the head is inclined slightly to conform to the inclination of the thread 3 on the container. With the method illustrated, the metal in the bead i2 at the lugs is subjected to a minimum amount of strain, since the metal in the band it has already been stretched, as shown in Fig. 2, and such stretchmg minimizes the strain on the metal in striking in the lug, hence the lug 5 may be struck inwardly further to provide maximum projection for engaging with the container thread without danger of cracking or breaking the metal.

The strain on the metal is further minimized during the lug formation by reason of the fact that the bead is bent inwardly to swing about the outwardly flared portion of the skirt of the cap back to its original position. Stretching of the metal is minimized and hence the strain on the metal is decreased because bending subjects the metal to less strain than stretching. The arch construction occasioned by forcing the head of the cap upwardly at the lugs, as shown at [15 (Fig. 7) increases the strength of the lug and gives the caps greater holding power. The formation of the arch collapses the bead vertically and increases the resiliency of the lug. The resiliency of the lug is increased without impairing the strength thereof, by reason of the fact that the upper side it of the head on the side of the cap, is in effect a miniature spring board, the resiliency of which may be increased or decreased by the tightness of the roll of the bead. For example, the head, as shown in Fig. 5, may be rolled upwardly to a point where its free edge engages with the skirt of the cap, as shown in Fig. 5, or it may be rolled upwardly, as shown in Fig. 8, where the edges are spaced from the skirt of the cap to give even greater resiliency. It is to be noted also, that pressure on the top of the lug at it tends to unroll the lug which increases the distance the lug projects inwardly from the skirt of the cap and also increases the security of its engagement under the thread of the container. An important feature in the construction of the lug is the absence of sharp edges or projections. Sharp edges scratch the surface of glass like a glass cutter or a diamond causing it to crack or break. Further, the formation of flat or sharp folds in sheet metal frequently cracks the metal forming jagged projections which will scratch the glass. The present lug presents a rounded surface like that of a wire to the glass surface as shown at it in Fig. 5a. Such a lug will not scratch the glass.

In Fig. 5a, the operation of the lug on the container thread is shown in a greatly enlarged view. An examination of the figure illustrates the security of the engagement and the strength and resiliency of the lug. The strength of the lug tends to prevent the lug from riding over the container thread and the resiliency of the lug permits greater tolerances or variations in the position of the glass thread 4, without impairing the seal or placing excessive strains on the container thread. The caps are ordinarily applied to the containers by screw capping machines operated at a speed of about 120 seals a minute. The caps are screwed on much tighter than is possible manually. Breakage of a container may require the stopping of the sealing machine, and a considerable delay in operation. In some cases, a broken thread may not be noted and the impaired seal results in a spoiled package reaching the consumer. In Fig. 8 a flat cover is shown with a bead 13 to illustrate the application of the improved lug to caps with various cover constructions.

It will be seen that the present invention provides an improved, inexpensive method of making closures of the lug type, and that the resulting closure cap 'has advantages over existing caps. By reason of the fact that the edge of the cap is turned inwardly, the exterior of the cap will have a uniform color or coating, whereas, if the edge were turned outwardly the coating on the inside of the cap would be exposed adjacent the color on the outside of the cap. In many cases, the lacquer coating on the inside of the cap is different from that on the outside which gives a bead with an external portion of a color different from the rest of the external portions of the closure. Likewise, if the head is rolled outwardly and struck inwardly to form lugs, the skirt of the cap above the bead is struck inwardly and forms the upper side of the lug.

Such formation of the lug gives a surface in-,

clined inwardly and downwardly and a very rigid upper surface for the lug. By having the upper springy side of the inturned bead engage under the thread on the container, the strength of the lug is not impaired and greater resiliency is obtained to take up tolerances in the position of the thread on the glass container without impairing the security of the seal. The method is simple and inexpensive and imposes a minimum amount of strain on the metal by reducing to a minimum the amount of metal stretching required in forming the lugs.

As various changes may be made in the form, construction and arrangementof the parts herein without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

1. The method of making a closure cap, which method comprises forming a cup-shaped blank with a cylindrical annular band at the lower part thereof having a greater diameter than the upper portion of said blank, flaring slightly inwardly the lower edge of said annular band to facilitate the subsequent formation of an inturned closed bead, turning the inwardly flared lower edge of said annular band inwardly, upwardly and outwardly to form an inturned annular closed bead on the blank with the internal diameter of the cap at said bead being substantially the same as the internal diameter of the upper portion of said blank, and striking inwardly and upwardly from the exterior of the blank circumferentially spaced portions of said inturned bead to form retaining lugs substantially without indenting portions of th blank above the bead, the inward forming of the lugs from said inturned annular bead subjecting the metal adjacent said lugs to bending during the inward striking operation.

2. The method of making lug closure caps which method comprises forming a sheet metal cup-shaped blank with a cylindrical band at the lower edge thereof having a diameter greater than the diameter of the blank above the band, turning the lower edge of said band inwardly, upwardly and outwardly to form an inturned bead on the bottom of the blank, the internal diameter of which is substantially equal to the internal diameter of the normal portion of the blank, and forcing said inturned bead inwardly and upwardly at intervals about the circumference ther'of to form screw lugs with relatively smooth convex surfaces for engaging screw projections on a container without indenting the metal of the blank above the enlarged zone of the blank in the forming operation.

3. The method of making closure caps, which method comprises forming a sheet metal cupshaped blank with an annular band at the lower edge thereof having a greater diameter than the upper portion of said cup-shaped blank, turn-- me the lower edge of said band inwardly, upwardly and outwardly to form an inturned open bead, the internal diameter of which is substantially equal to the internal diameter of the normal portion of the blank, and swinging said bead inwardly at intervals about the circumference thereof until it is substantially at right angles to its original position with the inner side of the open bead in position to engage the underside of a thread projection on a container so that the open bead at the lugs may flex from open to closed position to form resilient screw means.

JOHN C. GIBBS. 

